Progressive forming method of product having varied cross-sectional length

Abstract

A progressive forming method of a product having a varied cross-sectional length in the direction of supply of strip material. A material is first drawn so that a portion which corresponds to the portion of the product having a cross-sectional length larger than the smallest cross-sectional length is processed. The material is elongated by an amount corresponding to the difference of the length from the smallest length. Operations that require no differential elongation in the direction of supply are all performed subsequently, since such operations do not require excess stock that must ultimately be scrapped.

I claim: 
     
       1. A method for producing, from a continuous strip of plastically deformable material, a plurality of products in the form of substantially U-shaped cross section channel members, each product having a varied cross-sectional length in a direction of supply of the strip of the material, said method comprising the steps of: intermittently supplying the strip of material along a plurality of processing zones spaced from each other in the direction of the supply of the material, and   successively subjecting the material in successive zones to various processing steps between successive supplying steps, which processing steps at least include drawing, slitting, forming, and cutting, for obtaining from the material products having a varied cross-sectional length in the direction of supply of the material, wherein the improvement comprises:   first drawing the material in such a manner that each portion of the material corresponding to a portion of the product having a cross-sectional length greater than the minimum cross-sectional length of the product is shaped by plastically elongating the portion of the material by an amount corresponding to a difference of the cross-sectional length of said portion of the product from the minimum cross-sectional length of the product;   after all drawing steps, slitting the material to form a slit which extends transversely to the direction of the supply of the material; and   finally, cutting the material along lines parallel to the direction of supply of the material, to separate the obtained product from the remainder of the strip of the material, wherein the edges produced by said slitting transverse to the direction of the supply of the material are the total final edges of the product in the form of a U-shaped section channel member in said transverse direction, thereby attaining a scrap-less process in the direction of supply of the material.   
     
     
       2. A method according to claim 1, wherein the method comprises, after the slitting step, bending the material to form a flange portion of the product. 
     
     
       3. A die apparatus for producing, from a strip of material being intermittently supplied, a product in the form of a substantially U-shaped cross section channel member having a varied cross-sectional length in the direction of supply of the material, said apparatus comprising: a first plate member extending in the direction of supply of the material;   a second plate member extending parallel to the first plate member;   a means for causing the first and second plates to be moved toward each other; and   a die means arranged between the first and the second plate members, said die means having a plurality of processing stations spaced from each other in the direction of supply of the material, where various types of processing steps, including at least drawing, slitting, forming, and cutting, are simultaneously effected when the first and second members are moved toward each other;   the arrangement of the processing stations being such that the station for the drawing step is arranged as the first processing station in the direction of supply of the material, said die means for said drawing station comprising means for clamping the material transversely to the direction of supply before and behind a portion of the material to be drawn and means for differentially plastically elongating said portion of the material to be drawn, whereby a portion of the material corresponding to a portion of the product having a cross-sectional length larger than a minimum cross-sectional length of the product is plastically elongated, such that the slitting station is arranged downstream of the final drawing station to form a slit in the material which extends transversely to the direction of the supply of the material, and such that the cutting station is arranged as the last station to cut the material along lines parallel to the direction of supply of the material, for separating the obtained product from the remainder of the strip of the material, wherein the edges produced by said slitting in the direction of the supply of the material are the total final edges of the product in the form of a U-shaped cross section channel member in said transverse direction, thereby attaining a scrap-less process in the direction of supply of the material.   
     
     
       4. A die apparatus according to claim 3, wherein the means for differentially plastically elongating the portion of material to be drawn comprises a drawing die connected to the first plate and a drawing punch connected to the second plate. 
     
     
       5. A die apparatus according to claim 4, wherein said means for clamping the material transversely before and behind a portion of the material to be drawn comprises: a holder having a hole through which the drawing punch passes and   a spring means for urging the holder toward the drawing die so that the material subjected to the drawing process is positively held.   
     
     
       6. A die apparatus according to claim 3, wherein said die means further comprises a plurality of die sets corresponding to the stations for effecting slitting, forming, and cutting, each of said die sets comprising a first working member connected to the first plate member and a second working member connected to said second plate. 
     
     
       7. A die apparatus according to claim 6, wherein the first working member of the die set for slitting comprises a first cutter having an edge extending transversely to the direction of supply of the material and connected to the first plate, and the second working member of the die set for slitting comprises a second cutter having an edge extending transversely to said direction of supply of the material, said edges cooperating with each other to form the slit. 
     
     
       8. A die apparatus according to claim 6, wherein the first working chamber of the die set for forming comprises a stamping die connected to the first plate, and the second working member of the die set for forming comprises a stamping punch connected to the second plate, said die and punch cooperating to form a flange portion of the product. 
     
     
       9. A die apparatus according to claim 6 wherein the first working member of the die set for cutting comprises a first cutting means connected to the first plate and having a pair of parallel spaced edges extending in the direction of supply of the material and the second working member of the die set for cutting comprises a second cutter means connected to the second plate and having a corresponding pair of parallel spaced edges extending in the direction of supply of the material, said pair of edges of the first cutting means cooperating with the corresponding pair of edges of the second cutter means for separating the finished products from the material.